A total of 253 hydrocarbon-oxidizing bacterial
isolates were achieved from eight Antarctic surface seawater
samples enriched on diesel oil at 4°C. Isolates were
screened by ampliWed ribosomal DNA restriction analysis
prior to 16S rRNA gene sequencing. Sequences were compared
to those in available databases using the Basic Local
Alignment Search Tool network service to determine their
approximate phylogenetic aYliations. The majority of the
isolates were aYliated to the Actinobacteria (75.9%) and
the Gamma-Proteobacteria (22.9%). The Alpha- and Beta-
Proteobacteria represented 0.8 and 0.4% of total isolates,
respectively. The Actinobacteria were predominantly allocated
to the genera Arthrobacter, Cryobacterium and Rhodococcus.
The Gamma-Proteobacteria were mainly found
to be related to the genus Pseudomonas. Conversely, the
Alpha- and Beta-Proteobacterial isolates shared the highest
degree of sequence identity with unclassiWed bacteria.
DiVerences in the distribution of the detected phylotypes
were observed among the analyzed samples. Isolates representing
each phylotype were selected for further characterization,
including phenotypic assays and screening for the
growth ability in the presence of individual hydrocarburic
substrates as the sole supplied carbon and energy source.
Isolates possessed diVerent patterns of substrate utilization.
Aliphatic hydrocarbons supported the growth of a higher
number of isolates than aromatics. Results conWrm the ability
of our Antarctic marine bacteria to utilize hydrocarbons
at low temperature and therefore suggesting that isolates
with diVerent substrate speciWcities can act in nature as a
consortium in the utilization of complex hydrocarburic
mixtures.

A total of 253 hydrocarbon-oxidizing bacterial
isolates were achieved from eight Antarctic surface seawater
samples enriched on diesel oil at 4°C. Isolates were
screened by ampliWed ribosomal DNA restriction analysis
prior to 16S rRNA gene sequencing. Sequences were compared
to those in available databases using the Basic Local
Alignment Search Tool network service to determine their
approximate phylogenetic aYliations. The majority of the
isolates were aYliated to the Actinobacteria (75.9%) and
the Gamma-Proteobacteria (22.9%). The Alpha- and Beta-
Proteobacteria represented 0.8 and 0.4% of total isolates,
respectively. The Actinobacteria were predominantly allocated
to the genera Arthrobacter, Cryobacterium and Rhodococcus.
The Gamma-Proteobacteria were mainly found
to be related to the genus Pseudomonas. Conversely, the
Alpha- and Beta-Proteobacterial isolates shared the highest
degree of sequence identity with unclassiWed bacteria.
DiVerences in the distribution of the detected phylotypes
were observed among the analyzed samples. Isolates representing
each phylotype were selected for further characterization,
including phenotypic assays and screening for the
growth ability in the presence of individual hydrocarburic
substrates as the sole supplied carbon and energy source.
Isolates possessed diVerent patterns of substrate utilization.
Aliphatic hydrocarbons supported the growth of a higher
number of isolates than aromatics. Results conWrm the ability
of our Antarctic marine bacteria to utilize hydrocarbons
at low temperature and therefore suggesting that isolates
with diVerent substrate speciWcities can act in nature as a
consortium in the utilization of complex hydrocarburic
mixtures.